A nurse is reviewing a patient’s medications before administration. Which drug-to-drug interactions will most concern the nurse in a patient with a history of heart failure and a potassium level of 5.5 mEq/L?

Choice A reason: Metoprolol (beta-blocker) and furosemide (loop diuretic) are commonly used in heart failure. Furosemide may lower potassium, counteracting hyperkalemia (5.5 mEq/L), and metoprolol doesn’t significantly affect potassium. This combination poses less risk for hyperkalemia exacerbation, making it less concerning than potassium-sparing combinations. Choice B reason: Furosemide promotes potassium excretion, potentially reducing hyperkalemia (5.5 mEq/L), while enalapril (ACE inhibitor) may increase potassium. However, furosemide’s effect often offsets enalapril’s, making this combination less likely to worsen hyperkalemia significantly compared to two potassium-sparing drugs, so this choice is less critical. Choice C reason: Captopril (ACE inhibitor) and spironolactone (potassium-sparing diuretic) both increase potassium levels by reducing aldosterone activity, exacerbating hyperkalemia (5.5 mEq/L). In heart failure, this combination risks severe hyperkalemia, causing arrhythmias, making it the most concerning interaction requiring close monitoring or adjustment. Choice D reason: Amlodipine (calcium channel blocker) and propranolol (beta-blocker) primarily affect blood pressure and heart rate, not potassium levels. Their interaction may cause bradycardia or hypotension but doesn’t worsen hyperkalemia (5.5 mEq/L), making this combination less concerning for the patient’s current electrolyte status.